1. Field of the Invention
The present invention relates generally to an information server system. More specifically, the invention relates to a data transmission system for a client accessing multimedia data accumulated in a world wide web (WWW) server on an internet or so forth.
2. Description of the Related Art
Conventionally, servers, such as for WWW are adapted for access through a high speed line, such as local area network (LAN) or so forth. For this reason, data amount per one screen of display means is significantly large.
Therefore, when access is made to such server through low speed line, such as radio mobile terminal, substantial time is required for reception. Thus, the user of the radio mobile terminal has to wait for substantial period.
Therefore, some currently existing WWW servers perform a process of thinning of data or so forth for showing data without irritating the user by nominally avoiding lowering of response period for the user using the low speed line. However, in the current status, speeding of information display for the user of low speed line is achieved merely by eliminating image data or by using a progressive display to display rough image at first and then progressively transmitting detail of the image.
As a multimedia communication system, in which, after negotiation of a center with a distant station depending upon a medium, such as a telephone receiver (TEL), a facsimile machine (FAX), a personal computer (PC), which the user uses, data transformation adapting to the medium is performed so that the transmission side can perform data transmission without paying attention for kind of the medium at the reception side, has been disclosed in Japanese Unexamined Patent Publication (Kokai) No. Heisei 2-22356, for example. The communication system proposed in the above-identified publication is illustrated in FIG. 7. Each of the terminals for communication has a system construction adapted for communication with distant station through a center 111.
When data transmission is performed from the PC terminal, for example, at first, call is made to the center 111 for authentication of the transmitting user, and then ID of the distant station is input. The center retrieves the medium held by the distant station based on the input ID to terminate the call at telephone receiver. Then, the center 111 sends a voice message requesting selection of a medium. In response to this, a receiver at the distant station selects the desired medium for reception and sends a response through a push button (PB).
The center 111 is responsive to the receiver's response to perform data transformation for the selected medium. Then, data is transmitted to the distant station.
On the other hand, in Japanese Unexamined Patent Publication No. Showa 63-40488, for example, there has been disclosed an image transmission system for a television conference system which can transfer a high density image at the same channel speed as that for transmitting image data for television conference.
Conventionally, when a terminal connected to a radio data communication network or an ordinary telephone circuit through a low speed modem attempts to browse information of the WWW server or so forth, it takes a quite long period for receiving data containing image and voice. In the viewpoint of the user of the terminal, slow response is irritating.
As a general solution, there are two ways, (1) data dedicated for low speed line is prepared for the server, and (2) data is thinned.
These methods encounter a common problem in that data cannot be processed depending upon transmission capacity of the line.
Furthermore, in the above-mentioned method of (1), two kinds of data have to be prepared for each page. Therefore, while this method is relatively easy to realize, large storage capacity becomes necessary for a hard disk in the server.
On the other hand, in case of the method of (2), function means performing thinning process becomes necessary in or out of the server. Only univocal thinning based on a given rule, such as "image data is not transmitted", can be done. Therefore, in certain cases, it is possible to transmit data different from intention of author who prepared the data.